Smartsheet Group Management arbitrarily changes contacts' names

This is a weird one.

I have added a (male) contact called Chris to my contacts.

His correct name is showing in the contacts list.

When I add him to a group, I find and select him (still with the correct name).

However, when I save after adding him to the group, Smartsheet is changing his name to Christina.

Not great, and I need to iron this out before releasing the solution to the client.

I have tried deleting and re-adding in contacts and in groups, but same result.

Anyone else had this issue, please?